A method for inspecting a cold expanded fastener hole in a structural part to confirm that the hole has been expanded by a desired amount involves determining the degree to which the hole has been expanded as a function of the out-of-plane deformation in material surrounding an entrance or exit of the hole formed as a result of the cold expansion process. Out-of-plane deformation at either of the entrance or exit is compared to a model constructed from an array of experimentally or analytically determined out-of-plane deformation profiles for a hole with the same, or substantially the same, dimensions subjected to varying degrees of cold expansion. The degree of expansion of the hole is derived based on this comparison.